... will not go away until satisfied !
miggy say "blog idea like erection" because ...
... always happening at inconvenient or inappropriate times
... sometimes seems to be leading up to something but ends in disappointment
... acting on impulse can have disastrous repercussions
... intended recipient rarely in same mood at same time
... care is needed to avoid getting pregnant with anything you won't want to look after later
... sometimes happens in response to questionable or unexpected stimuli
... will let you think of nothing else until it is satisfied
... occasionally causes unduly or embarrassingly passionate outbursts that come back to haunt one
... is awful when taken too seriously or not seriously enough
(in fact, this article itself is perhaps a good example of what happens when it "seems like a good idea at the time") 